1. Field of the Invention
The present disclosure relates to total air temperature (TAT) probes or sensors. More particularly, the present disclosure relates to TAT probes subjected to the effects of in-flight icing.
2. Description of Related Art
Modern jet powered aircraft require very accurate measurement of outside air temperature (OAT) for inputs to the air data computer, engine thrust management computer, and other airborne systems. For these aircraft types, their associated flight conditions, and the use of total air temperature probes in general, air temperature is better defined by the following four temperatures: (1) Static air temperature (SAT) or (TS), (2) total air temperature (TAT) or (Tt), (3) recovery temperature (Tr), and (4) measured temperature (Tm). Static air temperature (SAT) or (TS) is the temperature of the undisturbed air through which the aircraft is about to fly. Total air temperature (TAT) or (Tt) is the maximum air temperature that can be attained by 100% conversion of the kinetic energy of the flight. The measurement of TAT is derived from the recovery temperature (Tr), which is the adiabatic value of local air temperature on each portion of the aircraft surface due to incomplete recovery of the kinetic energy. Recovery temperature (Tr) is obtained from the measured temperature (Tm), which is the actual temperature as measured, and which differs from recovery temperature because of heat transfer effects due to imposed environments.
Conventional TAT probes, although often remarkably efficient as TAT sensors, sometimes face the difficulty of working in icing conditions. Traditional TAT probes utilize a forward facing inlet scoop. During flight in icing conditions, water droplets, and/or ice crystals, are ingested into the TAT probe where, under moderate to severe conditions, they can accrete around the opening of the internal sensing element. An ice ridge can grow and eventually break free, clogging the sensor temporarily and causing an error in the TAT reading. To address this problem, conventional TAT probes have incorporated an elbow, or bend, to inertially separate these particles from the airflow before they reach the sensing element.
In addition, traditionally, anti-icing performance is also facilitated by heater elements embedded in the housing walls. Unfortunately, external heating also heats the internal air flow which, if not properly controlled, provides an extraneous heat source in the measurement of TAT. This type of error is commonly referred to as deicing heater error (DHE) or correction for DHE. Further, to overcome more severe icing conditions, the heating elements must achieve higher temperatures resulting in more power required to deice.
Some solutions for these challenges have been described in U.S. Pat. No. 7,357,572, U.S. Pat. No. 8,104,955, and U.S. Pat. No. 7,828,477, each of which is incorporated by reference herein in its entirety. Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is an ever present need in the art for improved TAT probe configurations. The present disclosure provides a solution for these problems.